Method of and apparatus for making articles



V. D. BARKER Dec. 19,'1939.

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FIG.

24 24- INVENTOP V. D. BARKER A TTORNEY Patented Dec. 19, 1939 Search Room UNITED STATES PATENT OFFICE RIETHOD OF AND APPARATUS FOR MAKING ARTICLES Virgil D. Barker, Westfield, N. J., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 10, 1937, Serial No. 130,070

2 Claims. (Cl. 140-71) the same reference numerals are applied to identical parts in the several gures and in which Fig. 1 is a broken view in side elevation of a device for forming and setting a grid electrode;

5 In certain kinds of apparatus dependent upon Fig. 2 is a section on the line 2-2 of Fig. 1; 5 electron streams, a grid electrode may be used Fig. 3 is a view similar to Fig. 2 after the comprising a flat helix of metal wire supported stretching operation; upon two or more substantially rigid wires or Fig. 4 is a section on the line 4--4 of Fig. 1; posts each lying along a generatrix or element Fig. 5 is a View similar to Fig. 4 after the l of the cylindrical surface which is enveloped by stretching operation; 10 the helix. In some such instances a filament is Fig. 6 is a broken side view of an unstretched positioned within the helix, comprising a wire grid; extending in one or more flat loops or coils ori- Fig. 7 is a broken edge view of an unstretched ented in a plane substantially parallel to and begrid;

l tween the flat sides of the helix. The lament Fig. 8 is a broken side view of a grid after 15 itself, thus formed and disposed, is substantially stretching; flat and occupies a portion of space of substan- Fig. 9 is a broken edge View thereof; tially uniform thickness, but the members used Fig. 10 is an enlarged broken detail edge View to support the filament between and yet out of of a portion of a stretched grid;

contact with the wires of the grid, must gener- Fig. 11 is a corresponding side view thereof, 20

ally be thicker and so will tend to approach the and grid more closely than the lament proper. Fig. 12 is a broken side view of a portion of An object of the present invention is to proan electron tube assembly including a grid as vide a method and apparatus for making a grid, shown in Figs. 8 and 9.

which shall afford sufficient space for other ele- The principal embodiment of the invention 25 ments to be housed within the grid without herein disclosed is a method of making a grid danger of accidental contact therewith or harmelectrode such as is disclosed in Figs. 8, 9 and ful approach thereto. 12. The grid comprises a pair of spaced, paral- One embodiment of. the invention as a method lel, rodlike, metal supports 2D and 2l, and a metal comprises steps of winding a strand of metal, Wire 22 Wound in a dat helix about the two sup- 30 capable without rupture of a suicient degree of ports. The supports and Wire may be made of elongation, about a pair of spaced, parallel, rodany metals, pure or alloyed in any way, approprilike supports in a flat helix, securing the turns ate to the subsequent intended use of the grid. of the helix to the supports at the intersections, The wire, however, must have sucient capacity forcing the supports apart to stretch and set the for elongation without rupture to endure the 35 coils of the helix, and simultaneously stretching stretching to which it will be subjected as hereone or more coils at one portion only of the helix inafter described. In one instance, in practise, transversely of the flat helix as well as parallel SHDDOIS 0f Substantially Dure nickel and a Wire thereto. of substantially pure molybdenum were found to Another embodiment of the invention as an be Satlsfactolfyg l 40 apparatus presents a device for stretching and In the prehmnary Steps of Wmdmg the Wire on setting the coils of an electrode such as described, the supports' 1t m2y-be found preferable to me" the apparatus including means to support the form thlsupports Withhspaqed nltches 23 (Flgs electrode supports in spaced parallelism, means 10 and to recelve t e Wlre t e Walls of the 15 to force the electrode supports apart whereby to notches bel-ng Subsequently staked down as at 45 24, over the wire to clamp the latter tightly in the force the helix coils of the electrode to assume Supports and to become .set in a longer and narrower form, The article Shown in Fig 6 and 7, has the Wire and means to simultaneously prevent one or more 22 Wound m Substantially uniform flat cons on coils of the helix at one portion thereof only the Supports 20 and 2|l the distance apart A of 6o from becoming narrower.

Other objects and features of the invention will appear from the following detailed description of one embodiment thereof taken in connection with the accompanying drawings in which the supports (Fig. 6) being somewhat less than their intended final distance C from each other (Fig. 8), and the width B of the coils of the helix (Fig. 7) being somewhat greater than the intended with D of a majority of the coils (Fig. 9). 55

To carry out the method of the invention, a device such as shown in Fig. 1 may be used. This comprises a base 38 to stand on or be secured to a bench, table or other support not shown, and has a vertically upstanding, principal supporting member 3|, the latter having a vertically oriented guide slot 32 therein. A tapering wedge 33 lies against and is vertically slidable on the flat front face of the member 3|, and has a rearwardly oiset rectangular guide portion 34 positioned in and guided by the slot 32. The left and right edges 35 and 36 of the wedge 33 may preferably be doubly bevelled, as indicated in Fig. 4. The left edge 35 is guided in and supported by the complementarily shaped right edge of a guide plate or member 31 rigidly secured on the front face of the support 3|. A coacting guide member 38 receives the edge 36 in its complementarily formed left edge, and is mounted to be horizontally slidable on the front face of the support 3|, in a suitable housing 39 secured to the member 3|. A spring 48 is provided to press the guide member 38 yieldingly to the left and thus to hold the wedge 33 against the guide member 31.

A fixed grid receiving post 4I is mounted on or formed integral with the member 31. The convexly rounded left vertical edge of this post has a groove 42 dimensioned to receive and support the grid support 20 (Fig. 4); and the right vertical edge of the post is formed as a continuation of the right edge of the member 31 and receives and supports the left edge of the wedge 33. A movable grid receiving post 43 is mounted on or formed integral with the member 38 and its convexly rounded right vertical edge is formed with a groove 44 dimensioned to receive and support the grid support 2| (Fig. 4). The left edge of the post 43 is a sloping continuation of the left edge of the member 38 and is formed to receive the right edge of the wedge 33.

The lower portion, 45 and 46 respectively, of each of the posts 4| and 43 is of uniform thickness irom front to back substantially equal to the interior width B of the coils of the helix 22 as originally wound and as shown in Figs. 6 and 7. This thickness is maintained upwardly from the bottom of the posts to a distance predetermined by the number of coils of the finished grid which are to have this interior dimension.

The remaining upper portions of the posts 4| and 43 are formed with outer portions 41 and 48 respectively of thickness from front to back substantially equal to the predetermined desired internal width D of a part of the coils of the nished grid. The remaining portions 49 and 5D of the posts 4| and 43 are thinner than the portions 41 and 48 are substantially of like thickness with the wedge 33.

An operating lever is pivotally secured, as at 52, on the at front face of the member 3|, and, as at 53, to the wedge 33. An adjustable stop 54 ls provided to accurately adjustably limit the downward motion of the outer arm of the lever 5| and thus both the upward motion of the Wedge 33 and the consequent spreading of the posts 4| and 43. The outer lever arm may be held up by a spring 55.

It may be advantageous to subject the grid structure shown in Figs. 6 and '1, which will be termed a raw grid for the purposes of this specification, to a suitable annealing operation as a preliminary step, e. g. the raw grid may be heated in a reducing atmosphere such as hydrogen to a temperature dependent upon the material of the grid, for the double purpose of destroying or driving on? surface contaminations and of reducing each part of the grid to a uniform physical state.

With the lever 5| in the position shown in Fig. 1, i. e. with the posts 4| and 43 at their nearest approximation to each other, the annealed grid is turned upside down and slipped down over the posts 4| and 43, the grid supports 20 and 2| sliding in the grooves 42 and 44, until the grid is positioned on the posts 4| and 43 as shown in Figs. 1, 2 and 4. The parts of the device of Fig. 1 are so proportioned and arranged that the unstretched grid iits smoothly but not loosely into this position on the device.

The outer arm of the lever 5| is then forced down, preferably with smooth steady motion, until it is stopped by the stop 54. The lever drives the wedge 33 up and forces the member 38 and its post 43 to the right a predetermined distance farther from the xed member 31 and its post 4|. The coils 222 of the grid, which embrace the post portions 45 and 46 as shown in Fig. 4, are thus forced to assume the form shown in Fig. 5 in which their length has increased from A to C while their width remains unchanged at the value B since the post portions 45 and 45 are of thickness B. 'Ihe remaining coils |22 of the grid, embracing the post portions 41 and 48, are also forced to increase in length from A to C, but are simultaneously allowed to decrease in width from B to D (Figs. 2 and 3), since the post portions 41 and 48 are themselves of thickness D.

Preferably the various dimensions involved are so proportioned and related that the sum total of the increase A to C and decreased B to D effects a surlicient increase in length of each half coil embracing 41 and 48 to stress the material of the wire 22 beyond its elastic limit. Hence each of these coils |22, after the stretching operation will be permanently set in its new form. At the same time the stretching of the coils 222 which embrace the portions 45 and 46 is more severe, since these are subjected to the same increase in length while being permitted no decrease in width. Hence the parts of the device of Fig. l are further so dmensioned that while the coils |22 are stressed beyond the elastic limit of the Wire, the more heavily stressed coils 222 are not brought to the rupture point. In the case of the grid now under consideration, the molybdenum wire has an elongation between 15% and 20% while the actual stretch in the coils |22 is roughly 101/2% and that in the coils 222 is about 121/ It may be advantageous to have the coils of the wire 22 clamped into the supports 20 and 2| in the manner disclosed, or to have them secured to the supports in some similar fashion,

especially if the preliminary annealing step be omitted, since this forces each half coil to be stretched uniformly with and independently of the others, thus ensuring substantially uniform physical condition upon the coils |22 relatively to each other and upon the coils 222 relatively to each other.

When the spring 55 is permitted to raise the lever 5| again, the spring 48 will force the member 38 and post 43 towards the member 31 and post 4|, whereupon the stretched grid can be easily drawn upwardly off the posts. 'I'he stretched grid then has the form and dimensions shown in Figs. 8 and 9 as compared with those of the unstretched or raw grid shown in Figs. 6 and 7.

The particular grid herein disclosed is intended for use in a vacuum tube whose relevant related parts only are shown assembled in Fig. l2. wherein 20, 22, l22, 222 are the stretched grid, 56 is a iilament positioned within the coils |22 and supported on a hook 51 positioned within the fractionally wider coils 222, and 58 is a plate of sheet metal surrounding the grid and lament, these parts being supported by a gallows-like structure 59, 59, 60. It is the hook 5l, wider of necessity than the lament 5B which, in this instance, necessitates the widening of the coils 222 as compared with the coils |22.

A characterizing feature of the invention, Whether considered as a method of making an article, or an apparatus' for applying the method, is the fact that during the process the strand 22 is stressed beyond its elastic limit so that it is set in its nal desired form since its physical character is that of material released from tensile stress above its elastic limit and it has no elastic tendency to depart from its final form.

The embodiments of the invention herein disclosed are illustrative only and may be departed from and modified in many Ways without departing from the spirit and scope of the invention as pointed out in and limited only by the appended claims.

SElVCn 00m What is claimed is:

1. An apparatus for treating a grid electrode comprising a metal strand formed in connected loops substantially equal in size secured to spaced supporting members, which apparatus comprises spaced elements to receive a grid electrode and having wide portions and narrow portions, and means to move the elements relative to each other a sufficient distance to simultaneously stretch the loops adjacent the wide portions without decreasing their width and decrease the width of the loops adjacent the narrow portions without stretching them and continue to move the elements to further stretch the iirst stretched loops and stretch the narrowed loops beyond their elastic limits.

2. A method of treating a grid electrode comprising a metal strand formed in connected loops substantially equal in size secured to spaced supporting members, which method comprises the steps of stretching certain of the loops without decreasing their width, simultaneously therewith narrowing the width of the other loops, and subsequently continuing the stretching of the rst stretched loops and stretching the narrowed loops 

